An unmanned Russian spacecraft carrying nearly 3 tons of supplies arrived at the International Space Station Monday (Feb. 11) less than six hours after blasting off.

The robotic Progress 50 resupply ship docked with the orbiting lab at 3:35 p.m. EST (2035 GMT) Monday after launching from Baikonur Cosmodrome in Kazakhstan at 9:41 a.m. EST (1441 GMT). Such unmanned cargo trips have traditionally taken about two days.

The Progress 50 spacecraft is packed with about 2.9 tons of supplies for the space station's six-man Expedition 34 crew. On Saturday (Feb. 9), the station astronauts discarded an older unmanned cargo ship, called Progress 48, in order to make room for Progress 50.

Progress 50, meanwhile, is delivering about 764 pounds (346 kilograms) of propellant, 110 pounds (50 kg) of oxygen and air, 926 pounds (420 kg) of water and about 3,000 pounds (1,360 kg) of spare parts, science gear and other supplies, according to a NASA description.

The Russian Federal Space Agency's Progress spacecraft are disposable vehicles similar in design to its three-segment Soyuz crew capsules, but with a propellant module in place of the central crew return capsule on the Soyuz.

Progress vehicles are designed to be disposable and are intentionally ditched into Earth's atmosphere at the end of their mission. Robotic resupply ships for the station built by Europe and Japan are also disposed of in the same way.

The only robotic supply ship for the space station that can return supplies back to Earth is the Dragon space capsule built by the private spaceflight company SpaceX.

Dragon space capsules visited the space station twice in 2012, with the next one slated to launch from Florida atop SpaceX's Falcon 9 rocket in March. Dragon vehicles are equipped with a heat shield to protect them during re-entry and are built for ocean splashdown landings in order to return experiments and other gear to Earth.

Tariq Malik

Tariq joined Purch's Space.com team in 2001 as a staff writer, and later editor, covering human spaceflight, exploration and space science. He became Space.com's Managing Editor in 2009. Before joining Space.com, Tariq was a staff reporter for The Los Angeles Times. He is also an Eagle Scout (yes, he has the Space Exploration merit bage) and went to Space Camp four times. He has journalism degrees from the University of Southern California and New York University. To see his latest project, you can follow Tariq on Google+, Twitter and on Facebook.